The present invention relates in a general manner to fluid loading and/or unloading systems, in particular for vessels transporting such fluids. A preferred application area is the transfer of liquefied natural gas between a loading and/or unloading crane installed on the ocean bed and an oil tanker moored near this crane.
Examples of such loading and/or unloading systems are described in particular in the documents FR-A-2 469 367 and EP-0 020 267. These systems include a device for transferring fluid between a loading jib and a coupling means provided on the vessel. The transfer device comprises a system of multiple articulated segments of fluid pipe of concertina or deformable diamond-shape type actuated by cable, the ends of the system being respectively connected by means of bends and rotary joints to sections of pipe fixed to the jib and to the sections of pipe intended to be connected to the coupling means. At least some of these bends are fixed to a support suspended on the jib.
The present invention aims at improving certain aspects of this type of system.
According to a first aspect, the present invention proposes a device for transferring fluid between a loading jib having at least one pipe section fixed to the jib and a coupling means comprising a system of multiple articulated segments of fluid pipe of concertina or deformable diamond-shape type and actuated by cable, at least one pipe section intended to be connected to the coupling means, each pipe section fixed to the jib or intended to be connected to the coupling means being connected to one end of the system of articulated segments by means of a bend and rotary joints, the bend being fixed to a support suspended on the jib, which device is characterized in that each end of the system of articulated segments is fixed to a second support mounted movably in rotation by means of a bearing on the support of the bend onto which the end is connected, concentrically with the rotary joint connecting the end to the bend.
The use of two concentric rotations allows the functions of support and joining to be disassociated in rotation. Thus the rotary joints of the ends of the system of articulated segments are isolated from the forces acting on these segments. This is particularly useful when transferring liquefied natural gas because these rotary joints or rotations are then subjected to a temperature of xe2x88x92160xc2x0 C. It is therefore necessary to limit the stress on these rotations. Such a mounting also enables balancing forces to be taken up directly on a structure for supporting articulated segments when this device for transferring fluid is provided with balancing systems.
The following are preferential conditions, possibly combined:
the device for transferring fluid includes a structure for taking up the weight of the system of multiple articulated segments carrying each pipe section intended to be connected to the coupling means and movably mounted in rotation by means of at least one bearing on the first support carrying each bend connected to a pipe section intended to be connected to the coupling means, each bearing being concentrically arranged on the rotary joint connecting a pipe section intended to be connected by coupling means to a bend, which weight take-up structure includes a tapered centering piece adapted to cooperate with a complementary piece of the coupling means;
the support carrying the connecting bend or bends to the section(s) of pipe fixed to the jib is suspended from the jib by means of struts, each of which is movably mounted in rotation, by means of a bearing on this support, concentrically with the connecting rotary joint(s) of the bend(s) on the pipe section(s) fixed to the jib.
Due to these conditions, none of the rotary joints situated on the upper and lower ends of the system of articulated segments are subjected to mechanical loads or stresses, in particular those connected to the mass of the system of articulated segments and to the accelerations to which these segments are subjected.
Because of the retraction phenomena produced during the transfer of liquefied natural gas, an annular free space preferably separates each associated rotary joint of the bearing, in the case of such an application.
In order to have access the fittings of the rotary joints, the support of the system end is advantageously equipped with a square-shaped piece, each end of the system of articulated pipe segments being fixed to one of the corresponding branches of a square-shaped piece and connected to the bend carried by the bend support by means of a supplementary bend fixed in a movable manner to this system end and connected to the bend of the bend support by a concentric rotary joint on a bearing connecting the other branch of the square-shaped piece to the bend support.
According to another original aspect within the scope of the present invention, the fluid transfer device is suspended from a jib pivotally tiltable on a jib support which is pivotally mounted in azimuth on a fixed base mounted on a platform, a first set of multiple pipe segments connects one part of the pipe carried by the jib to a pipe part fixed to the jib base and running to the bottom of the support and a second set of multiple pipe segments extends at the bottom the part of the pipe running along the support of the jib to the platform, the first and second sets of segments being configured and articulated to each other by means of rotary joints so as to permit the tilting movement of the jib on the jib support and the rotation of the jib support on its base, the pipe part running along the jib support as well as the first and second sets of segments being exterior to any substantially closed part of the support or the jib support.
Such conditions make it possible to avoid the installation of pipework inside an enclosed or badly ventilated space, which could have serious consequences in the case of an accidental leakage of liquefied gas.
In addition, it is possible to arrange the segments in the connection zone between the jib arid jib support such that they do not lead to the pipework rising which could prove detrimental to the circulation of fluid. In fact, such an arrangement facilitates in particular the drainage of fluid by gravity.
Moreover, all of the connection segments are easily accessible for maintenance.
More generally, such an arrangement of the connection segments between the jib and the jib support on the one hand and this jib support and the platform on the other are characterized by the simplicity of its design and consequently its low manufacturing and assembly costs, in particular for the crane.
According to another original aspect within the scope of the present invention, the fluid transfer device is suspended from a jib pivotally mounted and inclined on a jib support which is pivotally mounted in azimuth on a fixed support, the multiple articulated pipe segments form a series of two articulated diamonds the two respective angles of which are opposed at the vertex, the intermediate segments of pipe forming these two angles being joined together at their intersection by an articulation connected by a first set of cables and pulleys to a first set of free-balancing counterweights mounted movably in a longitudinal direction along the jib support whilst the support of the bends connecting the ends of the lower segments of the deformable diamonds to the pipe sections intended to be connected to the coupling means, is connected by a second set of cables to a second balancing counterweight controlled hydraulically and mounted movably in longitudinal direction on the jib support.
The implementation of two sets of balancing counterweights acting at different points on the structure of the multiple articulated segments allows the balancing forces intended to act on this structure to be adjusted precisely and, consequently, the loads, to which the rotary joints connecting the articulated segments to each other are subjected, to be limited in optimal fashion.
Such a balancing system also facilitates the connection of the fluid transfer device to the coupling means and the disconnection of the same transfer device.
To facilitate as much as possible the connection of the fluid transfer device to the coupling means, the pulling cable intended to allow this fluid transfer device to extend in order to connect it to the coupling means, is wound onto a winch mounted on the above-mentioned structure for the taking up of weight.
Advantageously, this winch, as well as the hydraulically controlled winch of the above-mentioned second set of balancing counterweights, are adapted to be controlled at a constant speed and a constant tension during the extension or retraction of the fluid transfer device.
By adjusting control of the winches, it is thus possible to ensure that the pulling cable is always taut, both during the phase of connection of the fluid transfer device to the coupling means and during the disconnection phase.
Consequently, it is possible to apply a maximum limit on the parasitic balancing phenomena of the fluid transfer device and to avoid impacts at the moment when the fluid transfer device comes into contact with the coupling means for the purpose of connecting them.